Mechanical interlock



Oct. 18, 1955 E. WILLIAMS 2,721,236

MECHANICAL INTERLOCK Filed Jan. 13, 1953 f7? ver? tor Ewes t M//'///'@ ms,

United States Patent MEcrrArucAr ENTERLQCK Ernest Williams, Pittsiieid, Mass assignor to General Electric Company, a corporation of New York Application January 13, 1953, Serial No. 331,005 Claims. (Cl. 200-50) This invention relates to a mechanical interlock, and more particularly, to an interlocking arrangement between two switches whereby only one of the two switches can be closed at any given instant, the other switch remaining open.

As will appear later, my invention has a great number of applications. It can be used with electrical and nonelectrical equipment. However, for purposes of best illustrating my invention its use in the electrical transformer art will be discussed.

in the transformer art it is not unusual to switch from one incoming line to another. Where the transformer can be placed on either of two incoming lines there is always a danger that the apparatus might accidentally be placed simultaneously on both incoming lines. This would result in overloading the apparatus and injuring or possibly destroying it.

It is an object of my invention to provide interlocking means between two switches whereby both switches can never be in the closed position simultaneously.

It is a further object of my invention to provide interlocking means between two cutout switches, each controlling an incoming line to a transformer, whereby both cutout switches can never be in the closed position simultaneously to place the transformer on both incoming lines, said interlocking means cooperating with the circuit breaker switch of the transformer so that the circuit breaker switch can be closed only when both cutout switches are locked in the open position or when one of the cutout switches is locked in the open position and the other cutout switch locked in the closed position.

It is further object of my invention to provide interlocking and cooperating means between two cutout switches and a circuit breaker switch whereby either cutout switch can be operated only when the circuit breaker is in the open position.

My invention comprises a cam carried by each of two switches and a slide bar cooperating with said cams Whereby said switches can never be simultaneously closed.

My invention also comprises a cam carried by each of two cutout switches, each cutout switch controlling an incoming line to a transformer, and a slide bar mechanism cooperating with said cams whereby said cutout switches can never be simultaneously closed, and a captive key lock for said slide bar mechanism cooperative with the circuit breaker switch of the transformer whereby said cutout switches cannot be operated unless the circuit breaker is locked in the open position, and said circuit breaker switch cannot be closed unless both of said cutout switches are locked in the open position or one of the cutout switches is locked in the open position and the other cutout switch locked in the closed position.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing.

In the drawing, Figure 1 is a perspective view of my device with both cutout switches locked in the open position. Figures 2 and 2a are top and front views respectively, of my device with the left hand cutout switch locked in the closed position and the right hand cutout switch locked in the open position. Figures 3 and 3a are top and front views respectively, of my device and of the positions the parts assume in going from the Figure 1 position to the Figures 2 and 2a position. Figures 4 and 4a are top and front views respectively, of my device with the left hand cutout switch locked in the open position and the right hand cutout switch locked in the closed position. Figures 5 and 5a are top and front views respectively, of my device and the positions the parts assume in going from the Figure 1 or Figures 2 and 2a position to the Figures 4 and 4a position.

Referring now to the drawing, and more particularly to Figure 1, there is shown therein left and right hand mechanisms for actuating left and right hand switches. The parts on the right hand side are duplicates of the parts on the left hand side, so for purposes of clarity, like parts on both sides will be given like reference numerals except that the right hand numerals will be primed.

As earlier stated, my invention has a great variety of applications, electrical as well as non-electrical. This will appear as the description proceeds. However, for purposes of teaching my invention, the following description is immediately concerned with the application of my invention to the transformer art.

In Figure l, casings or enclosures .l and 1 carry the cutout switch mechanisms. For instance, within each of the casings 1 and 1 may be located two line terminals. A cap 2 and 2, rotatably mounted in casings 1 and i may carry suitable contact elements so as to open or close the line. The details of the cutout switches have not been shown since this constitutes no part of the invention and a variety of switches can be used in practicing my invention. Caps 2 and 2 have mounted thereon T-shaped brackets 3 and 3'. The side ends of the brackets 3 and 3 are bent normal to the plane of the brackets and fastened to the caps, as by welding. To the T-shaped brackets are fastened, as by welding, U-shaped brackets 4 and 4'. Through the upright legs of the U-shaped brackets 4 and 4- are passed hand levers 5 and 5. To the end of the vertical leg of T-shaped brackets 3 and 3 are connected rods 6 and 6. It will be noted that the rods 6 and 6' are connected to the other cutout switches so that levers 5 and 5 will actuate sets of cutout switches. That is, by manipulating handles 5 and 5' a group of transformers or transformer phases can be simultaneously placed on either of two incoming nnes.

To caps 2 and 2 are connected fiat generally sectorlike cams 7 and 7. These cams are identical in configuration and rotate with the switch mechanisms to open and close positions. The cams have an outer curved edge or outer arc portion with the angularly spaced end edges or radii defining portions of each cam disposed from each other by an obtuse angle of about As will appear more clearly later, and as shown in Figure 1, when the left and right hand mechanisms are locked in the open position, the similar end edges or radial edge portions 24 and 24 of cams 7 and 7' will lie in front of opposite end portions of a locking slide bar 18 and parallel to slide bar 18 when the latter is positioned equidistant from the two switches and cams, That is, the bar 18 will be abuttingly disposed with respect to end edges 24 and 24' so as to lie in the path of rotation or movement of cams 7 and 7. in the arc portion of each cam is a notch 10 and 10'. The notches are disposed about 90 degrees from the similar end edges 24 and 24'. In the closed position of the switches, as will appear more clearly hereinafter, and as shown in Figures 2 and 4, the cams will have been rotated to a position wherein each cam and its notch will be positioned between the switch on which it is mounted and the adjacent end of the slide bar 18.

Cams 7 and 7' are welded to side bars 8 and 8 which in turn are clamped to caps 2 and 2 by bolts 8 and 9'. The caps 2 and 2 have suitable non-circular surfaces to facilitate this clamping.

The structure previously described is mounted on a suitable switchboard 11. On this same switchboard is mounted a bracket 12. To the upper portion of bracket 12 is fastened a plate 13. Plate 13 carries on its upper surface a captive key lock 14. The plunger 15 of the captive key lock extends downwardly through plate 13. A captive key lock is an article that can be readily purchased on the market, and is a lock wherein the key can be removed from the lock only when the lock is in the locked or closed position. That is, the key can be removed only if the plunger 15 is protruding.

To the bottom surface of plate 13 is fastened a plate 16. Protruding forwardly from plate 16 are two bolts 17 which carry and guide the locking slide bar 18 in its sideways sliding movement. Slide bar 18 has a suitable guide slot 19 so that slide bar 18 can be moved sideways. On the top of slide bar 18 are two lugs 28 that define a detent or notch 21. in the locked position of captive key lock 14 the plunger 15 will extend through plate 13 into notch 21 so that slide bar 18 cannot be moved.

Slide bar 18 carries 'a pointer 22. The tip of the pointer is aligned with the midpoint of notch 21. Carried by switchboard 11 is a bracket 23 that has a dial thereon with three marks. When the tip of pointer 22 is aligned with the middle or Zero mark of dial 23 the slide bar 18 will be positioned midway between the left and right hand switches and notch 21 will be able to receive plunger 15 so that slide bar 18 and cams 7 and 7' are locked against movement.

In Figure l the left and right hand cutout switches are locked in the open position. That is, edges 24 and 24' of cams 7 and 7' are parallel to and in front of slide bar 18. Neither of the switches can be actuated since the slide bar 18 and cams 7 and 7' are abuttingly disposed. Since the opposite ends of bar 18 lie in the path of movement or rotation of the cams, edges 24 and 24' will strike the bar ends and prohibit rotation of levers or 5 to operate the switches.

To place the transformer on either the left hand or right hand line, the key that operates the captive key lock must first be removed from the circuit breaker switch of the transformer. The details of the circuit breaker switch have not been shown since it is not part of this invention and a multiplicity of switches can be used. However, it is contemplated that the circuit breaker switch used have a captive key lock as earlier discussed and the arrangement be such that the key can be removed only when the circuit breaker is locked in the open position, which is conventional structure well known in the art. Since the key can be removed from the circuit breaker switch only if the circuit breaker is in the open position, the cutouts can be operated only if the circuit breaker switch is open. The wisdom of such an arrangement lies in the fact that the cutouts typically are not constructed to withstand the high sparking attendant to completing or opening a circuit. Therefore, this is accomplished at the circuit breaker prior to operating the cutouts. Consequently, assuming one desires to place the transformer on one of the lines, he must first open the circuit breaker before he can remove the key from the circuit breaker. After removal of the key from the circuit breaker one is free to operate the cutouts since 4 he has the key with which the lock 14 can be unlocked to free the slide bar 18.

Assuming one desires to operate either the left or right hand cutout, he must first insert the key in captive key lock 14 to raise plunger 15 out of notch 21. Once plunger 15 is raised slide bar 18 is free to be moved to the left or right depending upon which cutout is to be closed. To close the left hand cutout slide bar 18 must be moved to the right so that earn 7 can be rotated counterclockwise. See Figures 3 and 3a. As lever 5 is rotated counterclockwise can '7 also rotates counterclockwise. When the left hand cutout switch is finally in the closed position, the notch 18 in cam 7 will be opposite the left hand end of slide bar 18. At this instant the circuit breaker switch cannot be closed since the key is captivated by lock 14. It ill be remembered that the key can be removed from lock 14 only if lock 14 is locked, that is, plunger 15 is protruding downward. Plunger 15 can protrude downward only when slide bar is positioned equidistant from and midway between the left and right hand switches. Therefore to close the circuit breaker the slide bar 18 must be moved to the left to its zero position. See Figures 2 and 2a. When this is done, the left hand end of slide bar 18 will enter notch 10 in cam 7. When this is accomplished the right hand end of slide bar 18 will not have cleared edge 24 of cam 7. Only now can the key be removed since the notch 21 is now positioned beneath the plunger. To remove the key the lock 14 must be locked. Thus, if key 14 is removed so as to close the circuit breaker switch so the transformer can be placed on the left hand line, the left hand cutout is locked in the closed position and the right hand cutout is locked in the open position. Thus, both cutouts cannot be simultaneously closed.

To attain the position shown in Figures 4 and 4a wherein the right hand cutout is in the closed position and the left hand cutout is in the open position the plunger 15 must be raised so that slide bar 18 can be manipulated sideways. This means that the circuit breaker must again be opened in order to free the key for insertion into lock 14. After the plunger 15 is raised the slide bar 18 is moved to the right out of notch 18. Then left hand cutout is rotated clockwise to the open position wherein edge 24 is parallel to and in front of slide bar 18. Now slide bar 18 can be moved to the left so that edge 24' will not abut slide bar 18 as lever 5 is rotated clockwise to place the right hand cutout in the closed position. See Figures 5 and 5a. After the right hand cutout is rotated clockwise to the closed position notch 10 in cam 7 will be opposite the right hand end of slide bar 18. Then slide bar 18 can be moved to the right to enter groove 10'. When this occurs notch 21 will be beneath plunger 15 so that the lock 14 can be locked in order to remove the key to operate the circuit breaker into closed position. However, at this point the left hand end of slide bar 18 protrudes into the path of rotation of cam 7 so that the left hand cutout is also locked in the open position. Thus, both cutout switches cannot be simultaneously closed.

To get from the Figures 4 and 4a position to the Figures 2 and 2a position the circuit breaker switch must be opened. After the key is extracted from the circuit breaker the plunger 15 can be raised, slide bar 18 is moved to the left, cam 7 is rotated counterclockwise, slide bar 18 is moved to the right, see Figures 3 and 3a, cam 7 is rotated counterclockwise until notch 10 is opposite the left end of slide bar 18, and then slide bar 18 is moved to the left so the left end of slide bar 18 enters notch 10. Now slide bar 18 is positioned equidistant from and midway between the left and right hand switches and notch 21 is in line to receive plunger 15. Now the lock 14 can be locked and the key removed from lock 14 to operate the circuit breaker switch into closed position.

It should be noted that the left and right hand switches cannot be simultaneously actuated. Only one switch can be operated at a time. To open the left hand switch the slide bar 18 must be moved to the right. See Figures 3 and 3a. Then the left hand switch can be actuated, but slide bar 18 will be so positioned that the right hand switch cannot be actuated while the left hand switch is moved. The right hand end of bar 18 will always lie in the path of rotation of cam 7' as long as the left hand witch is free to operate. In order to operate the right hand switch, the left hand switch must be locked against movement in order for slide bar 18 to clear the cam 7' of the right hand switch. Thus, the slide bar 18 is always abuttingly disposed with respect to one of the cams 7 and 7 so that both switches cannot be operated at the same time.

It will now be apparent that my invention has a great number of applications. For instance, my invention can be used with electrical apparatus other than transformers where there are two switches and it is desired to have safety means to guard against simultaneous closing or operation of both switches. Further, my invention can be practiced with non-electrical apparatus. For instance, my invention can be used in a gas or hydraulic fluid system where there are two valves and it is desirable to safeguard against simultaneous closing or operation of both valves. Also my invention is not necessarily limited to a situation where it is sought to safeguard against simultaneous closing of two switches or valves. Obviously, it is also applicable to a situation where simultaneous opening of two switches or valves is to be prohibited. For these reasons, I do not intend that my invention shall be limited to the specifically shown and described embodiment of my invention. What I believe to be the full scope of my invention I have defined with particularity in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A safety mechanism for ensuring that two switches are not simultaneously in a closed position, comprising a slide bar positioned between said switches and slidable endwise between said switches, an identical cam carried by each of said switches, said cams having an identical end edge lying in front of said slide bar when said switches are in an open position and said slide bar is positioned equidistant from said switches whereby both of said switches are locked open, each of the said cams having a notch therein, each of said cams and its notch lying between the switch on which it is mounted and an adjacent end of said slide bar when said switch is in a closed position, said slide bar having a length suflicient to protrude one of its ends into the cam notch of a closed witch while the cam end edge of an open switch is in front of the opposite end of said slide bar whereby when one of said switches is locked closed the other of said switches is locked open.

2. In an apparatus having two control devices each movable to an open and close position, locking means for prohibiting said control devices from being in a close position simultaneously, said means comprising an elongated slide bar located between said control devices and movable endwise between said control devices toward and away from said control devices, said control devices each carrying a like cam with a notch therein and said cams being movable with said control devices to open and close position, said cams when said control devices are both open having an identical end edge lying in front of opposite ends of said slide bar when said slide bar is positioned equidistant from said control devices whereby both of said control devices are locked open, said cams when one of said control devices is open and the other closed being positioned so that the end edge of the open control device cam is located in front of an adjacent slide bar end while said slide bar is positioned midway between the control devices with an opposite end of said slide bar entering the notch of the cam mounted on the closed control device whereby said one control device is locked open and said other control device is locked close, said slide bar having a notch therein positioned midway between said control devices when said slide bar is equidistant from said control devices, and a captive key lock having a plunger adapted to enter said slide bar notch only when said slide bar is positioned equidistant between said control devices, the key of said captive key lock being removable only when said plunger enters said slide bar notch whereupon said slide bar is locked against endwise movement.

3. In a mechanism having two rotatable control devices each rotatable to an open and close position, locking structure for locking said control devices both in an open position or one of said control devices in a closed position and the other in an open position, said locking structure prohibiting said control devices from being simultaneously actuated or placed in a closed position simultaneously, said locking structure comprising an approximately 120 sector-like cam mounted on each of said control devices and rotatable therewith, and a looking bar mounted between said control devices and slidable therebetween endwise, said cams being identically shaped and having a curved outer portion disposed between two radially extending edges, said cams when said control devices are both in an open position and said looking bar is positioned equidistant between said control devices having a similar radially extending edge thereof disposed in front of and parallel to opposite end portions of said locking bar so that said control devices are both locked in an open position, said cams each having a groove therein in the outer curved portion thereof disposed approximately degrees from said similar radially extending edges, said control devices when in a closed position having the grooves in said cams lying opposite adjacent ends of said locking bar, said locking bar when one of said control devices is closed being slidable towards said closed control device so that its adjacent end will enter the groove in the cam carried by said closed control device while the other end of said locking bar continues to lie in the path of rotation of the other cam to retain the other control device locked in an open position.

4. A mechanical interlock comprising two spaced cams and a single interlocking elongated slide bar cooperative therewith, said cams being identical in configuration, fiat, generally sector-like, and each disposed in a horizontal plane, each of said cams having an outer arc edge portion defined between two radially extending edge portions spaced from each other by an angle of about each of said cams movable from a first position to a second position and vice versa, said slide bar positioned between said cams in said plane and slidable endwise therebetween toward one of said cams and away from the other of said cams and "ice versa, each of said cams when in said first position having one of said radially extending edge portions thereof disposed in front of opposite end portions of said slide bar when said slide bar is positioned equidistant of said two cams whereby each of said cams is locked in said first position, each of said cams having a notch in said outer arc edge portions disposed about 90 from said one radially extending edge portion, each of said cams when in said second position having said notches thereof disposed along a line coincidental with the lengthwise dimension of said slide bar opposite to an adjacent end of said slide bar, said lengthwise dimension having a predetermined length whereby when a single one of said cams is moved to said second position and said slide bar is positioned equidistant of said cams an end of said slide bar adjacent said single one cam is disposed within the notch of said single one cam in abutting relationship with an interiormost portion of said single one cam notch while an end of said slide bar adjacent another of said cams is still disposed in the path of movement of said another cum from said first position to said second position whereby neither of said cams can be simultaneously actuated to said second position and whereby when either one of said cams is locked in said second position the other of said cams is locked in said first position.

5. A mechanical interlock comprising a left-hand and a right-hand movable cam spaced from each other and a single elongated lengthwise slidable cam interlocking bar cooperative therewith, said cams having an identical sector-like configuration and both disposed in a horizontal plane, each of said cams having an outer arc edge portion defined between two generally radially extending edge portions spaced from each other at an angle of about 120, said bar positioned between said cams in said plane and slidable endwise towards one of said cams and away from the other of said cams and vice versa, each of said cams rotatably movable about an axis perpendicular to said plane extending through the apex of said radially extending edge portions thereof from a first position to a second position and vice versa, said bar when positioned equidistant of said cams having opposite end portions thereof abuttingly disposed in the path of movement of the outer arc edge portions of both of said cams and when moved endwise having one of said end portions disposed in the path of movement of one of said are edge portions and the other of said end portions clear of the path of movement of the other of said are edge portions whereby said cams are prohibited from simultaneous movement, said cams when both in said first position having one radially extending edge portion thereof disposed in front of an adjacent end portion of said bar when said bar is positioned equidistant of said cams whereby said cams are locked in said first position, a

notch in each of said locked cams formed in the arc edge portion thereof about forwardly of said one radially extending edge portion thereof, said left-hand cam rotatable counterclockwise from said first position to said second position and said right-hand cam rotatable clockwise from said first position to said second position, each of said cams when in said second position having said notch thereof disposed opposite to an adjacent end of said bar, said bar having a predetermined length whereby when a single one of said cams is disposed in said second position when said bar is positioned equidistant of said cams an end of said bar adjacent said single one cam is abuttingly disposed with respect to an interiormost portion of the notch of said single one cam while another end of said bar is abuttingly disposed with respect to the one radially extending edge portion of another of said cams whereby when either one of said carns is locked in said second position the other of said cams is locked in said first position.

References Cited in the file of this patent UNITED STATES PATENTS 560,751 Potter May 26, 1896 1,482,051 Turner Jan. 29, 1924 1,850,302 Hoelscher Mar. 22, 1932 2,080,964 Forstrom May 18, 1937 2,085,642 DeJong June 29, 1937 2,166,061 Kirk July 11, 1939 2,438,691 Armantrout Mar. 30, 1948 2,580,338 Wallace et a1. Dec. 25, 1951 FOREIGN PATENTS 560,217 Great Britain Mar. 24, 1944 

